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Review – TeleVue Ethos Eyepieces

The TeleVue Ethos eyepiece line has redefined the ultra-widefield observing experience.

Introduction

It took some time for me to realize that a seismic shift was about to take place in amateur astronomy when TeleVue announced a new eyepiece design at the 2007 Northeast Astronomy Forum. I had been using the Nagler series for almost a decade; and like most other owners of this venerable eyepiece line, couldn’t really see how TeleVue could make significant improvements to wide-field observing.

I balked at trying the 13mm Ethos when it was released due to its hefty price and the fact that I didn’t need another medium-power eyepiece. But as TeleVue introduced more focal lengths to the Ethos catalog, I felt compelled to take a chance on at least one of them.

The 2010 release of the 21mm Ethos made my decision easier. Here was an eyepiece that I could directly compare to my 22mm Nagler. With the aid of the software Stellarium, I was able to see that the Ethos would offer an additional half degree to the fov at essentially the same magnification. And so, I started saving up the $795 required to buy the eyepiece (it’s $854 today). In 2013, I bought the 21mm and 6mm Ethos.

Design

Televue has been more discrete about how they created this marvel, so I’ll just directly quote from their website that “the Tele Vue Ethos is essentially multiple eyepieces, delivering the true field size of a longer focal length, narrower apparent field eyepiece with the benefits of higher power and darker sky background.” Obviously, trade secrets are important in a competitive environment and no mention is given as to the number of lens elements or groups used in the Ethos line.

Review: This eyepiece certainly makes a big impression on you the first time you see it. The box it came in is absolutely huge and unwrapping it for the first time brought an unscripted “ooooh!” of satisfaction. It’s 7″ tall with the eyeguards attached and just as heavy as the 31mm Nagler, but less bulky and easier to hold with one hand.

Although the 21mm Ethos makes balancing the Baby-Q somewhat problematic on the Teegul Mount w/ Lapides Modification, it’s an absolute joy to look through. Ptolemy’s Cluster – M 7 looks amazing; as if it’s swimming in a sea of background stars with no edge to the field of view in sight, yet its stars are well resolved into tiny pinpoints of light. Objects that I would generally view with the 31mm Nagler for wide-field observing, like the Small Sagittarius Star Cloud – M 24, Scutum Star Cloud, and Cygnus Star Clouds, benefit from the increased magnification of the 21mm Ethos by bringing out fainter stars nestled within.

To give you an idea of just how profound an improvement the Ethos line is over the Nagler, let’s compare the Takahashi FCT-76 with a 22mm Nagler to the Takahashi FSQ-85ED with a 21mm Ethos:

That’s a lot more viewable area at an increased magnification. The benefit being what Televue refers to as the “Majesty Factor,” which they define as the “combining [of] a larger apparent field [yielding greater deep sky details] with smaller exit pupils [yielding fainter stars with darker sky background].”

Taking the Stellarium screenshots of the region around Lambda Sagittarii, both M 22 and M 28 can be seen in the same fov at 21x magnification through the Takahashi FSQ-85ED. The one key point to make about this fact is that each object lies at opposite ends of the fov; so while you can see both globular clusters in the same eyepiece at the same time, seeing them simultaneously is a bit of a challenge. That’s how wide the 21mm Ethos goes!

It has been said that the Ethos line provides a “cooler” hue to stars compared to the Nagler and Panoptic lines. I would describe the stellar colors instead as being more “balanced.” By that I mean stars which were more red-orange in the older eyepiece lines now appear distinctly orange in the Ethos. The same can be said of previously orange-yellow stars that now look flatly yellow, while white stars look exactly the same to me.

Eye Relief is comfortable at 15mm off the top compared to the Nagler series which has a little more per comparable focal length. The good news is that with the Ethos line, you quickly become accustomed to placing your head at the same position relative to the eyepiece. And there is no pincushion distortion whatsoever.

All-in-all, the 21mm Ethos is as good of a wide-field eyepiece as one could hope for.